Classically bag filtration devices consist of a housing, fluid inlet and outlet connections, an internally supported basket, a loosely fitting cylindrical cloth bag with a closed bottom and rigid ring-like upper rim, and, a hinged and bolted cover plate to retain the rim of the bag and to seal the pressure housing. Fluid under pressure is introduced into the vessel, allowed to pass through the bag in an inside-out mode, and, then exit through an isolated outlet port. Suspended solids in the incoming fluid that are of larger size than the openings of the filter bag are trapped inside the bag. As the solids plug the inner surface of the filter bag, the differential pressure across the bag will rise, and, when the maximum allowable pressure is reached, the filter system is shut down, the vessel vented and/or drained, the cover removed, the expanded bag removed, and, a new bag is reinstalled. Obviously the life of any particular bag depends upon the integrity of the bag seams, closures and seals, and, more importantly, the surface area of the bag itself.
Many innovations have been developed in an attempt to improve the bag insertion and the sealing of the top edge ring of the bag itself. Many innovations have been proposed to provide fluted or cogged surfaces within or around the bag retention mechanisms to allow the bag material to deform and thereby provide a modest increase in filtering surface area. Many or all work to some extent but they have not been universally accepted due to initial high costs, only modest increases in surface area, difficulty in manufacture, high maintenance costs, difficulty in assembly, and requirements for specially designed multiple parts and components. Secondly, there are presently many rigid pleated cartridges employed in pressure vessel filtering housings. These cartridges are usually integral units with rigid inner cores, pleated and encapsulated membrane packs, netted outer cages, rigid end caps, and, typically outside-in flow. The entire cartridge must be designed to withstand full differential pressures, and thereby, normally limited to modest diameters and lengths, and obviously, limited surface areas. Furthermore, to fabricate that type of rigid pleated cartridge for large diameters and/or for inside-out flows, additional and excessive reinforcement, is required, and thereby, precludes the manufacture of economical disposable cartridge element.
Furthermore, pleated and/or cylindrical elements, as presently available, are limited by the surface area of the pleated or cylindrical surfaces of the final filtering membrance. Even with progressive and/or progressive depth filtraton, the overall life of such elements is restricted by the surface area of the final filtering membrane since, in those configurations, much of the fine particulate in the fluid being filtered is allowed to progress all the way through the coarser filter media and lodge against the final finite filter membrane surface.
Therefore to retain the basic advantageous characteristics of bag filtration but to overcome the above mentioned deficiencies of said bag and rigid element filters, this invention addresses a novel filtering element that provides semi-rigid, one-piece inexpensive construction, greatly enhanced filtering area, and internal dirt retention, and that it can be readily adapted to existing bag filter housings or incorporated directly into newly designed or existing pressure filtering vessels for complete versatility of filtration purposes.